1. Field of the Invention
The present invention generally relates to electrical, condition responsive systems and methods. More particularly, this invention relates to a method and apparatus for detecting smoke in a monitored area using a sequence of digitized images of the area.
2. Description of the Related Art
Smoke detectors are very important safety devices that can provide an early warning of fire in a monitored area. Considerable efforts have been devoted to improving upon the technology used in smoke detectors as a means of increasing their usefulness and reliability.
One of the most commonly used methodologies for smoke detectors involves measuring the presence of aerosol particles at the location of a smoke detector's sensor. Such measurements are based either on light scattering phenomena or on the effects due to smoke particle interactions with an ionization current created within the detector. See Rattman, et al., U.S. Pat. No. 5,719,557.
A disadvantage of this approach is that its measurements are limited in terms of their sensing area since such detectors monitor for the presence of smoke only at those points that are in close proximity to the location of the detector's sensor. The successful detection of smoke in a monitored area using this technique greatly depends upon the rate of movement of smoke particles toward the detector's sensor which, depending upon the size of the monitored area, can be located a considerable distance from the initial source of any smoke.
To address this insufficient sample size problem, it has been suggested that air samples be collected at multiple locations in the monitored area and then to guide these samples to the location of the detector's sensor. See Knox, et al., U.S. Pat. No. 6,285,291. Although effectively increasing the extent of spatial sampling within a monitored area, this method has the disadvantage of requiring the installation of multiple sampling tubes at assorted locations throughout the monitored area.
Another approach for smoke detection has been to monitor the light scattering effect of smoke particles on a laser beam that is directed across a monitored area. Rather than just sensing smoke in just the relatively small vicinity of a single sensor, the laser beam approach effective senses for smoke along a line that can extended for a considerable distant throughout the monitored area. See Moore, et al., U.S. Pat. No. 3,973,852. However, a disadvantages of using such a laser beam approach is that, although it may effectively measure smoke conditions at more points within a monitored area that just those points in the vicinity of a single sensor, it still does not provided feedback on the smoke conditions at all or most of the points within the monitored area.
Despite the considerable prior art relating to smoke detectors, there is still a need for smoke detector methods and systems that can more effectively measure smoke conditions throughout the entire volume of a desired monitored area.